They did make seperate fan blades, suction, and push for the 310G. You'll probably have to go to Case Construction parts, and see which one will fit yours, or maybe they all fit, all models... whether either a gas, or diesel.
Here is the link for Case Construction :
CASE
Put your cursor on "Parts and Service", and a drop down menu will give you several selections. Click on 'Search for parts". Enter your model number and go from there. Fan and fan belt is down towards the bottom of the parts (scroll down to 141A page number to the left) listing. There are serial number breaks, so you'll need yours.
I copied and pasted the first serial nuumber run pusher fan part number, and chose the disel pusher fan part number. Coleman Equipment shows one, but no price. It says price available, after placing order. So either it is real expensive, or not available...
Here is a link to a salvage yard for crawlers.
Crawler Heaven | New Parts You may find one there by chance, as it says he has a/some 310G('s) Or may be able to help you find one.